Ashfield, Massachusetts, showcases "green" wastewater treatment plant.

• Author: Leue, Tom

The innovative wastewater treatment plant in Ashfield, Massachusetts, is the first municipal greenhouse-based wastewater treatment plant of its kind in the commonwealth. The Ashfield Wastewater Treatment Plant (AWWTP) serves the village of Ashfield in the Berkshire hills. First brought on-line in fall of 1996, the plant has currently about 165 household equivalents connected, some of which are seasonal, and it has capacity for up to 25,000 gallons per day (GPD). The process is advanced tertiary treatment, and the effluent usually meets the requirements for drinking water, although it is not used for that purpose.

This state-of-the-art plant is the culmination of a 25-year struggle by the townspeople to build an adequate treatment system. Ashfield was notified it was in violation of the Clean Water Act in 1972, as numerous houses and even the town school, town offices, and others disposed of wastewater with little or no treatment directly into a small stream that runs through the center of the town. Disease and unsightliness were constant concerns. It took 25 years for the town to turn this stream back into the South River, and now, for the first time in more than 200 years, the stream runs clean. Ashfield citizens will be holding a celebration of the South River in the fall of 1998, with a river clean-up to remove any lingering rusted metal or miscellaneous debris.

Several designs for a treatment system had been tried during this period, but none was actually built. Design engineers first proposed a community septic tank, but the state rejected that idea because it did not protect the groundwater. Later, a rotating biological contactor and an oxidation ditch were proposed, but were rejected by the town as obnoxious neighbors. Finally, the Board of Health researched alternative systems and presented this new technology to the townspeople. It was interesting, attractive, odor free, and had ancillary benefits, such as educational use, horticultural options, and it was very "green." The town voted 99 percent in favor of the greenhouse-based process.

The plant encompasses about 10,500 square feet of greenhouse space, plus a small administrative building. Municipal sewage flows in through a new collection sewer to storage tanks, where sodium bicarbonate is added to supplement the naturally low alkalinity, and after an average retention time of less than one day in a preliminary conditioning tank, it is pumped to the first greenhouse and into six...